The removal effect of natural and modified zeolites containing different heavy metals (Ni2+, Zn2+, Fe3+ and Cu2+) on pure cultures of Escherichia coli and Staphylococcus aureus in a solid medium was evaluated in this work. These experiments were carried out in a continuous mode treating municipal wastewater. Faecal coliform species and Pseudomonas aeruginosa were identified. The rate constants of heavy metal lixiviation were determined using a first order kinetic model. The removal effect of modified natural zeolites in both a solid medium and in continuous mode showed an increased elimination of the bacterial population. The results established a decreasing order of the removal effect as follows: Cu2+ > Fe3+ > Zn2+ > Ni2+. The best performance of columns was obtained for inlet bacterial concentrations below 10(6) cells/100 ml. Most of the identified bacterial species were affected by copper modified zeolites, although Serratia marcescens presented the highest sensitivity and Klebsiella pneumoniae the greatest resistance.
Recent discoveries have shown the presence of several shipwrecks and historical pieces submerged in the seacoast of the Yucatan Peninsula of Mexico. Within these remains, it is common to found objects manufactured in copper alloys that were part of the construction system of the vessel. For the present study, different surface analysis techniques were applied to tubular copper alloy objects collected in the wreck "El Tejas". The metallographic study allowed us to know not only the microstructure but also features over its manufacturing technique, as an example of nineteenth-century handmade production. SEM, EDX and XRF techniques allowed us know the elemental composition and establish the mechanisms of degradation of the different copper alloys in the seabed and evaluated a preservation method that consist on removing chlorine compounds by cleaning with pressure steam of distilled water.
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